linux-kernel - Re: [PATCH v3 10/30] perf clang: Add builtin clang support ant test case

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Date:   Mon, 5 Dec 2016 10:36:02 +0800
From:   "Wangnan (F)" <wangnan0@...wei.com>
To:     Arnaldo Carvalho de Melo <acme@...hat.com>, <ast@...com>
CC:     <lizefan@...wei.com>, <hekuang@...wei.com>,
        Ingo Molnar <mingo@...nel.org>, <linux-kernel@...r.kernel.org>,
        <pi3orama@....com>, <joe@....org>, Jiri Olsa <jolsa@...nel.org>,
        <acme@...nel.org>
Subject: Re: [PATCH v3 10/30] perf clang: Add builtin clang support ant test
 case

On 2016/12/2 23:44, Arnaldo Carvalho de Melo wrote:
> Em Sat, Nov 26, 2016 at 07:03:34AM +0000, Wang Nan escreveu:
>> Add basic clang support in clang.cpp and test__clang() testcase. The
>> first testcase checks if builtin clang is able to generate LLVM IR.
>>
>> tests/clang.c is a proxy. Real testcase resides in
>> utils/c++/clang-test.cpp in c++ and exports C interface to perf test
>> subsystem.
>>
>> Test result:
>>
>>     $ perf test -v clang
>>     51: Test builtin clang support                               :
>>     51.1: Test builtin clang compile C source to IR              :
>>     --- start ---
>>     test child forked, pid 13215
>>     test child finished with 0
>>     ---- end ----
>>     Test builtin clang support subtest 0: Ok
> While testing this I noticed that the perf binary got huge, can't this
> be done in some other way, i.e. using dynamic library?

I intentionally use statically linking because it is good for
smartphone: we can simply 'adb push' a statically linked perf
to Android.

The resulting ELF executable would be even larger if LLVM is
built with default setting.

In my setting the resuling 'perf' is less than 60MB:

  $ ls -s  ~/perf -h
  58M /home/wn/perf

  $ size  ~/perf
    text       data        bss        dec        hex    filename
  56931273    2950808    24108632    83990713    50198b9 /home/wn/perf

It is reasonable for me.

I think using dynamic clang and llvm libraries is possible but I
never tried it before. It depend on LLVM compiling. I think if
distro provides shared libraries then perf can utilize them
automatically. Let me check it today.

About the file size, I discussed with Alexei, he taught me a lot
on it. Maybe he or his ioVisor ex-colleagues can provide some
new idea?

Thank you.